1. Field of the Invention
The present invention relates to a chip-type solid electrolytic capacitor with a fuse and, more particularly, to a structure of a cathode terminal section with a fuse.
2. Description of the Related Art
Generally, a solid electrolytic capacitor is used in various electronic circuits, and is advantageous in that its failure rate is low. Once failure occurs, however, there will be many cases where short-circuiting occurs. When large short-circuiting current flows in such a case, a capacitor element may be heated up to be burnt out.
In order to prevent the capacitor element from being burnt out, which occurs with failure due to the excessive short-circuiting current, and in order to protect peripheral circuit elements, it is necessary to open the capacitor element in case of such short-circuiting.
For this purpose, conventionally, a solid electrolytic capacitor of the type in which a fuse is built in has generally been used. This solid electrolytic capacitor will hereinafter be referred to as "a solid electrolytic capacitor with a fuse".
FIGS. 4(a) and 4(b) are a perspective view and a cross-sectional view, respectively, showing the constitution of a conventional solid electrolytic capacitor with a fuse. In the solid electrolytic capacitor with a fuse, a capacitor element 1 is composed of an anode lead 2 and a cathode layer 3. An anode terminal 4 is connected to the anode lead 2. Further, the cathode layer 3 and a cathode terminal 5 are adhered to each other by an insulating adhesive 6. A fuse 7 is connected to the cathode layer 3 and the cathode terminal 5 by solder 8 so that the cathode layer 3 and the cathode terminal 5 are bridged to each other. Furthermore, the fuse 7 is covered with an elastic resin 9, and all of the elements referred to the above are armored by a molding resin 10.
The conventional chip-type solid electrolytic capacitor with a fuse, as described above, is of the constitution in which the cathode layer and the cathode terminal are electrically connected to each other by the fuse. With this arrangement, therefore, the conventional solid electrolytic capacitor with a fuse has the following disadvantages:
(1) The fuse and the capacitor element are directly connected to each other. Accordingly, when overcurrent flows to heat up the fuse disadvantageously, the heat indirectly melts the solder on the cathode layer so that the solder is thermally expanded to destroy the molding resin.
(2) The insulating adhesive is used for providing insulation between the cathode layer and the cathode terminal of the capacitor element. When the fuse is connected during the manufacturing process, however, the cathode layer and the cathode terminal may be in danger of short-circuiting to each other during a step in which the adhesive hardens. Accordingly, it is required that at least one of the cathode layer and the cathode terminal be preliminarily insulated.
(3) The capacitor element and the cathode terminal are apt to be exposed outside the molding resin, depending upon the connection between the anode lead and the anode terminal and the connection of the fuse. In addition, since the capacitor element per se is not necessarily constant in dimension and configuration due to the capacity and withstanding voltage, a position where the fuse and the cathode layer are connected to each other by soldering is therefore not constant, thus making it difficult to automatically solder the fuse.
As described above, in the conventional chip-type solid electrolytic capacitor with a fuse, the manufacturing step, particularly, the fuse connecting step will be troublesome and cumbersome. Thus, it is difficult to improve the reliability of the fuse to reduce the cost.